Scientists from the University of Western Ontario in Canada studied what happened when four patients in an intensive care unit died. They were all on life support, and the research team monitored their brain activity — measuring something called frontal electroencephalographic (EEG) recordings — when the machines were turned off.

The paper says three patients showed no further activity as soon as the life support machine was turned off, but something intriguing happened with the fourth patient — they appeared to give off the same kind of brain waves we experience when we're in a deep sleep, called "delta wave bursts."

The study was incredibly small to start with, looking at just four patients, and the results get even more narrow when you consider just one of them showed this activity.

The researchers are careful to note that they can't gain too much information from the results, but they did conclude death could be a unique experience for each person. This is because there were very few similarities between the brain activity of the four patients before and after their death.

Studies like these are interesting for medicine because they have the potential to help with the outcomes of transplant surgeries. They could also be important for understanding what happens to the body when we die, which could have implications for improving doctors' chances of bringing people back after near-fatal accidents.

Understanding what happens after we die is intriguing, but the Canadian team stress they can't really explain what happened in this new research. They mention in the paper that there's a possibility of a human or equipment error that falsely showed the brain activity, but as far as they know the equipment was working properly and no-one messed up.

"Further study of the [EEG] during the withdrawal of life-sustaining therapies will add clarity to medical, ethical, and legal concerns for donation after circulatory determined death," the researchers said.